Sensor assembly configured to sense target movement in first direction and insensitive to target movement in second and third directions orthogonal to first direction

ABSTRACT

A sensor assembly having a pair of sensors and a pair of sensor targets. Each of the sensors is an eddy current sensor that defines X, Y and Z axes that are orthogonal to one another such that the X-axes are aligned to a movement axis along which a structure is to be moved. The sensor targets are coupled to one another for common movement and are formed of an electrically conductive material that is configured to interact with a respective one of the eddy current sensors to cause the sensors to produce sensor signals that each vary in a distinct manner with movement of the targets parallel to the movement axis. The targets are configured such that their coordinated movement in a direction parallel to the Z-axes as they are moved along the movement axis has no effect on the determined location of the structure. A method is also provided.

FIELD

The present disclosure relates to a sensor assembly.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

There is need in the art for an inexpensive, reliable and accuratesensor to monitor the position of a component that is translated along amovement axis, particularly in the field of actuators for drivelinecomponents. In this regard, actuators for driveline components typicallypresent an environment that is not friendly to conventional sensors dueto large thermal extremes, the presence of lubricant, and potentiallythe presence of metallic particles that are suspended in the lubricant.Since these sensors must operate reliably over an extended period oftime, there is a desire to avoid the use of magnets in the sensors(e.g., Hall-effect sensors), since there is a possibility that metallicparticles could be attracted to the magnet of the sensor.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one form, the present disclosure provides a sensor assembly fordetermining a location of a structure that is translated along amovement axis. The sensor assembly includes a sensor mount, first andsecond sensors, and first and second targets. The first sensor iscoupled to the sensor mount and is an eddy current sensor that has afirst X-axis, a first Y-axis and a first Z-axis that are orthogonal toone another. The first X-axis is disposed parallel to the movement axis.The first sensor includes a first coil that is wound helically aroundthe first Z-axis. The second sensor is coupled to the sensor mount andis an eddy current sensor that has a second X-axis, a second Y-axis, anda second Z-axis that are orthogonal to one another. The second X-axis isparallel to the first X-axis. The second Z-axis is parallel to the firstZ-axis. The second sensor includes a second coil that is wound helicallyaround the second Z-axis. The first target is configured to be coupledto the structure for movement therewith. The first target is formed ofan electrically conductive material and is configured to interact withthe first sensor to produce a first sensor signal that has a firstmagnitude that varies proportionally with movement of the first targetalong the first X-axis. The second target is configured to be coupled tothe structure for movement therewith. The second target is formed of anelectrically conductive material and is configured to interact with thesecond sensor to produce a second sensor signal that has a secondmagnitude that varies proportionally with movement of the second targetalong the second X-axis. The first and second targets are configured sothat coordinated movement of the first and second targets withinpredefined limits in a direction parallel to the first and second Z-axesas the structure is moved along the movement axis is detectable from thefirst and second sensor signals.

In another form, the present disclosure provides a sensor assembly fordetermining a location of a structure that is translated along amovement axis. The sensor assembly includes a sensor mount, first andsecond sensors, first and second targets and a controller. The firstsensor is coupled to the sensor mount and is an eddy current sensor thathas a first X-axis, a first Y-axis and a first Z-axis that areorthogonal to one another. The first X-axis is disposed parallel to themovement axis. The first sensor includes a first coil that is woundhelically around the first Z-axis. The second sensor is coupled to thesensor mount and is an eddy current sensor that has a second X-axis, asecond Y-axis, and a second Z-axis that are orthogonal to one another.The second X-axis is parallel to the first X-axis. The second Z-axis isparallel to the first Z-axis. The second sensor includes a second coilthat is wound helically around the second Z-axis. The first target isconfigured to be coupled to the structure for movement therewith. Thefirst target is formed of an electrically conductive material and isconfigured to interact with the first sensor to produce a first sensorsignal that has a first magnitude that varies in a first predeterminedmanner with movement of the first target along the first X-axis. Thesecond target is configured to be coupled to the structure for movementtherewith. The second target is formed of an electrically conductivematerial and is configured to interact with the second sensor to producea second sensor signal that has a second magnitude that varies in asecond predetermined manner with movement of the second target along thesecond X-axis. The controller receives the first and second sensorsignals and responsively determines the location of the structure alongthe movement axis. The first and second targets are configured such thatcoordinated movement of the first and second targets in a directionparallel to the first and second Z-axes within predefined limits as thestructure is moved along the movement axis has no effect on the locationof the structure that is determined by the controller.

In a further form, the present teachings provide a method that includes:providing a structure that is movable along a movement axis; coupling asensor assembly to the structure, the sensor assembly comprising firstand second eddy current sensors and first and second targets that aremounted to the structure for movement along the movement axis; sensingthe first target with the first eddy current sensor and responsivelygenerating a first sensor signal; sensing the second target with thesecond eddy current sensor and responsively generating a second sensorsignal; and using the first and second sensor signals to determine alocation of the structure along the movable axis in a manner that isinsensitive to coordinated movement of the first and second targets in afirst direction that is perpendicular to the movement axis.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic top plan view of a sensor assembly constructed inaccordance with the teachings of the present disclosure;

FIG. 2 is a schematic right side view of the sensor assembly of FIG. 1;

FIG. 2A is a schematic illustration of the sensor assembly that depictseach of the eddy current sensors as including an RLC gate-oscillatorcircuit that generates a frequency output;

FIG. 3 is a sectional, partly schematic view of the sensor assembly ofFIG. 1 integrated into a vehicle driveline component having a clutch;

FIGS. 4 through 7 are views depicting alternately constructed portionsof the sensor assembly of FIG. 1, the alternately constructed portionsbeing first and second sensor targets; and

FIG. 8 is a view similar to that of FIG. 3 but depicting the sensorassembly constructed in accordance with the teachings of the presentdisclosure as employing first and second sensor targets that areconfigured in the manner depicted in FIG. 6 and mounted to asynchronizer.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With reference to FIGS. 1 and 2, a sensor assembly constructed inaccordance with the teachings of the present disclosure is generallyindicated by reference numeral 10. The sensor assembly 10 can include asensor mount 12, a first sensor portion 14, a second sensor portion 16and a controller 18. The sensor mount 12 can be any type of structure,such as a circuit board, to which the first and second sensor portions14 and 16 can be mounted.

The first sensor portion 14 can include a first sensor 22 and a firsttarget 24, while the second sensor portion 16 can include a secondsensor 26 and a second target 28. Each of the first and second sensors22 and 26 can include a coil 32 that is mounted to the sensor mount 12and configured to generate a magnetic field 36 when activated (i.e.,when receiving alternating current). Each of the coils 32 can beoriented such that it disposed along an associated Z-axis 40 thatextends perpendicular from a surface 42 of the sensor mount 12 to whichthe coils 32 are mounted. The wire of each coil 32 can be woundhelically about the associated Z-axis 40 of the coil such that the coils32 have a generally annular shape. Alternately, each of the coils 32 iswound in a helical manner that is parallel to the associated Z-axis 40and parallel to an axis that is perpendicular the associated Z-axis 40.In the particular example provided, each of the coils 32 is woundhelically about its Z-axis 40 in a manner that is elongated about itsY-axis 44 so that when viewed from a plane that includes its X-axis 46and Y-axis 44, the coils 32 are generally oval in shape.

The first target 24 can be formed of a plate-like piece of anelectrically conductive material that has opposite surfaces 50 and 52that are oriented perpendicular to the Z-axis 40. The first target 24 isconfigured to interact with the magnetic field 36 generated by the coil32 of the first sensor 22. More specifically, placement of the firsttarget 24 into the magnetic field 36 generated by the coil 32 of thefirst sensor 22 can induce eddy currents 54 in the first target 24. Theeddy currents 54 induced in the first target 24 can create an opposingmagnetic field 56 that can interact with the magnetic field 36 generatedby the coil 32 of the first sensor 22; the first sensor 22 can output afirst sensor signal that is responsive to the magnitude of the opposingmagnetic field 56. The first sensor 22 is configured so that themagnitude of the interaction between the magnetic field 36 and theopposing magnetic field 56 is dependent upon a distance between thefirst target 24 and the coil 32 of the first sensor 22 along the Z-axis40. The first target 24, however, is also configured to also render thefirst sensor 22 sensitive to the placement of the first target 24 alongthe X-axis 46. In this regard, the first target 24 can be shaped in amanner that varies the amount of the electrically conductive material inwhich the opposing magnetic field 56 is generated as a function of theplacement of the first target 24 along the X-axis 46. For example, thefirst target 24 can be shaped so that the output of the first sensor 22is ratiometric when the first target 24 is moved only along the X-axis46. In the particular example provided, the first target 24 defines agenerally V-shaped notch or aperture 60 that is formed through thematerial that forms the first target 24 and aligned such that the axis62 of the V-shaped notch 60 is disposed in a plane that includes theZ-axis 40 and the X-axis 46.

The second target 28 can be formed of a plate-like piece of anelectrically conductive material that has opposite surfaces 64 and 66that are oriented perpendicular to the Z-axis 40. The second target 28is configured to interact with the magnetic field 36 generated by thecoil 32 of the second sensor 26. More specifically, placement of thesecond target 28 into the magnetic field 36 generated by the coil 32 ofthe second sensor 26 can induce eddy currents 70 in the second target28. The eddy currents 70 induced in the second target 28 can create anopposing magnetic field 72 that can interact with the magnetic field 36generated by the coil 32 of the second sensor 26; the second sensor 26can output a second sensor signal that is responsive to the magnitude ofthe opposing magnetic field 72. The second sensor 26 is configured sothat the magnitude of the interaction between the magnetic field 36 andthe opposing magnetic field 72 is dependent upon a distance between thesecond target 28 and the coil 32 of the second sensor 26 along theZ-axis 40. The second target 28, however, is also configured to alsorender the second sensor 26 sensitive to the placement of the secondtarget 28 along the X-axis 46. In this regard, the second target 28 canbe shaped in a manner that varies the amount of the electricallyconductive material in which the opposing magnetic field 72 is generatedas a function of the placement of the second target 28 along the X-axis46. For example, the second target 28 can be shaped so that the outputof the second sensor 26 is ratiometric when the second target 28 ismoved only along the X-axis 46. In the particular example provided, thesecond target 28 defines a generally V-shaped notch or aperture 78 thatis formed through the material that forms the second target 28 andaligned such that the axis 80 of the V-shaped notch 78 is disposed in aplane that includes the Z-axis 40 and the X-axis 46.

The first and second targets 24 and 28 can be fixedly coupled to oneanother for common movement. For example, the first and second targets24 and 28 can be fixedly mounted to a structure 84 that is movable atleast along a movement axis 86 that is parallel to the X-axes 46. Thefirst and second targets 24 and 28 can be aligned in coordinated mannerrelative to the first and second sensors 22 and 26, respectively, suchthat the Z-axes 40 are parallel to one another, the X-axes 46 areparallel to one another and to the movement axis 86, the Y-axes 44 areparallel one another, and the axes 62, 80 of the V-shaped notches 60, 78are parallel to one another and aligned along the X-axes 46. In theparticular example provided, the structure 84 to which the first andsecond targets 24 and 28 are coupled is a piece of aluminum plate intowhich the first and second targets 24 and 28 are formed. It will beappreciated that the first and second targets 24 and 28 could be formedas discrete components that are mounted to another structure to reducecost and/or weight as desired. Moreover, it will be appreciated that thefirst and second targets 24 and 28 could be offset from one anotheralong the Z-axis 40 of the first sensor 22, and/or that the first andsecond sensors 22 and 26 could be similarly offset from one anotheralong the Z-axis 40 of the first sensor 22.

The controller 18 can be coupled to any desired structure, such as thesensor mount 12, and can be configured to receive the first and secondsensor signals and to responsively determine a position of the structure84 along the movement axis 86.

The second target 28 can be configured to interact with second sensor 26in a manner that is different from the manner in which the first target24 is configured to interact with the first sensor 22 so that the mannerin which the second sensor signal varies in response to movement of thestructure 84 along the movement axis 86 is different from the manner inwhich the first sensor signal varies in response to movement of thestructure 84 along the movement axis 86. In the particular exampleprovided, the V-shaped notch 78 of the second target 28 is orientedopposite to the V-shaped notch 60 of the first target 24 so thatmovement of the structure 84 along the movement axis 86 in a firstdirection is associated with enlargement of the width of the V-shapednotch 60 of the first target 24 along the Y-axis 44 of the first sensor22, and reduction of the width of the V-shaped notch 78 of the secondtarget 28 along the Y-axis 44 of the second sensor 26.

The V-shaped notch 60 in the first target 24 renders the first sensorportion 14 an absolute position sensor for positions along the X-axis 46within a predetermined range. Similarly, the V-shaped notch 78 in thesecond target 28 renders the second sensor portion 16 an absoluteposition sensor for positions along the X-axis 46 within thepredetermined range. Moreover, if there is no movement of the first andsecond targets 24 and 28 along the Z-axis 40 relative to the coils 32,the value of the output of one of the first and second sensors 22 and 26can be determined based on the value of the output of the other one ofthe first and second sensors 22 and 26 (i.e., the value of the secondsensor signal can be determined based on the value of the first sensorsignal and vice versa).

In situations where the first and second targets 24 and 28 move in acoordinated manner along the Z-axis 40, the values of the first andsecond sensor signals will be higher or lower (relative to their valueswhen there is no movement along the Z-axis 40) depending on whether thefirst and second targets 24 and 28 have moved toward or away from thecoils 32. As such, the values of the first and second sensor signalswill not relate to one another in the expected manner (i.e., as thoughthere is no movement along the Z-axis 40) but rather will include acommon offset. The controller 18 can be configured to identify theexistence of a common offset and to effectively remove the common offsetfrom the values of the first and second sensor signals to therebyisolate the portion of the first and second sensor signals that relatesto the absolute position of the structure 84 along the movement axis 86from signal noise that relates to movement of the structure along theZ-axis 40.

As an example, suppose that the values (y1, y2) of the first and secondsensor signals are related to the position (x) of the structure 84 alongthe movement axis 86 (within predefined limits) in a linear manneraccording to the formulas:y1=m(x)−b;andy2=b−m(x);where (m) is a predefined slope and (b) is a predefined constant. In asituation where the structure 84 is moved only along the movement axis86 and does not move along the Z-axis 40, the values of y1 and y2 willsum to zero (i.e., the value of y2 is the additive inverse of y1).Accordingly, the controller 18 can average the values of y1 and y2determine information relevant to the positioning of the structure 84along the Z-axis 40. For example, if the average is non-zero, thestructure 84 has been positioned at a location along the Z-axis 40 thatdeviates from a predefined location. Additionally, the absolute value ofthe average is indicative of the magnitude by which the position of thestructure 84 deviates along the Z-axis 40 from the predefined location,and the sign (positive or negative) of the average is indicative of thedirection along the Z-axis 40 that the structure 84 is located relativeto the predefined location.

Alternatively, the location of the structure 84 along the movement axis86 can be determined by dividing the value of one of the first andsecond sensor signals by the sum of the values of the first and secondsensor signals (e.g., the value of the first sensor signal divided bythe sum of the values of the first and second sensor signals). Becausethe first and second sensor portions 14 and 16 employ a dual sensorconfiguration with complementing outputs, the controller 18 can: a)determine the value of each of the first and second sensor signals, b)determine the sum of the values, c) determine a first ratio that isequal to the value of the first sensor signal to the sum of the values,d) determine a second ratio that is equal to the value of the secondsensor signal to the sum of the values, and e) determine the location ofthe structure 84 along the movement axis 86 based on the first andsecond ratios.

Construction of the sensor assembly 10 in this manner can be relativelyinexpensive, eliminates the need for calibration of the sensor assembly10, requires relatively little space for the packaging of the sensorassembly 10, and permits the axial location of the structure 84 to bedetermined along the movement axis 86 with accuracy that can be betterthan 0.5% regardless of changes in voltage, temperature or the presenceof vibration.

With reference to FIG. 2A, each of the first and second sensors 22 and26 can include an RLC gate-oscillator circuit that cooperates with theeddy current sensor to generate a frequency output that is dependent onthe magnetic field produced by the coils 32 of the first and secondtargets 24 and 26, respectively, and the opposing magnetic fields 56 and72 (FIG. 2).

In FIG. 3, the sensor assembly 10 can be employed to sense a position ofa clutch fork 100 that is moved by a linear actuator 102 along amovement axis 86. The clutch fork 100 is engaged to a synchronizer 104in a conventional manner and is employed for translating thesynchronizer 104 into and out of meshing engagement with a plurality offirst coupling teeth 108 that are coupled to a driven gear 110 forcommon rotation. Those of skill in the art will appreciate that thestructure 84 is the clutch fork 100 and that the first and secondtargets 24 and 28 (FIG. 1) are mounted directly to (or alternativelyformed in) the clutch fork 100. The linear actuator 102 can be any typeof device that is configured to translate the clutch fork 100 along themovement axis 86. In the particular example provided, the linearactuator 102 is a electromagnetically operated solenoid, but those ofskill in the art will appreciate that other types of linear motors,including fluid-powered cylinders, could be employed in the alternative.

While the first and second targets 24 and 28 (FIG. 1) have beendescribed as comprising V-shaped notches 60, 78 (FIG. 1), those of skillin the art will appreciate from this disclosure that the first andsecond targets 24 and 28 (FIG. 1) could be shaped differently. Forexample, the first and second targets could be shaped as taperedsurfaces as shown in FIGS. 4 through 7. In FIG. 4, the first and secondtargets 24 a and 28 a comprise sensing surfaces 120 and 122,respectively, that taper along the Z-axes 40 in a ratiometric manner. InFIGS. 5 through 7, the first and second targets 24 b and 28 b comprisefrusto-conical sensing surfaces 120 b and 122 b, respectively, thattaper in a radial direction. Configuration in this latter manner may beparticularly suitable for situations in which the structure 84 is alsorotatable about the movement axis 86 and the first and second targets 24b and 28 b are coupled to the structure 84 for rotation and axialmovement therewith.

In FIG. 8, the sensor assembly 10 b can be employed to sense a positionof a rotating synchronizer 104 that is moved by a clutch fork 100 and alinear actuator 102. The clutch fork 100 is engaged to a synchronizer104 in a conventional manner and is employed for translating thesynchronizer 104 into and out of engagement with a plurality of firstcoupling teeth 108 that are coupled to a driven gear 110 for commonrotation. Those of skill in the art will appreciate that the structure84 is the synchronizer 104 and that the first and second targets 24 band 28 b are formed on a portion of the synchronizer 104 that isdisposed on a side opposite the first coupling teeth 108.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A sensor assembly for determining a location of astructure that is translated along a movement axis, the sensor assemblycomprising: a sensor mount; a first sensor coupled to the sensor mount,the first sensor being an eddy current sensor having a first X-axis, afirst Y-axis and a first Z-axis that are orthogonal to one another, thefirst X-axis being disposed parallel to the movement axis, the firstsensor comprising a first coil that is wound helically around the firstZ-axis such that a first dimension across the first coil along the firstY-axis is larger than a second dimension across the first coil along thefirst X-axis; a second sensor coupled to the sensor mount, the secondsensor being an eddy current sensor having a second X-axis, a secondY-axis, and a second Z-axis that are orthogonal to one another, thesecond X-axis being parallel to the first X-axis, the second Z-axisbeing parallel to the first Z-axis, the second sensor comprising asecond coil that is wound helically around the second Z-axis such that athird dimension across the second coil along the second Y-axis is largerthan a fourth dimension across the second coil along the second X-axis;a first target that is coupled to the structure for movement therewith,the first target being formed of an electrically conductive material andbeing configured to interact with the first sensor to produce a firstsensor signal that has a first magnitude that varies proportionally withmovement of the first target along the first X-axis; and a second targetthat is coupled to the structure for movement therewith, the secondtarget being formed of an electrically conductive material and beingconfigured to interact with the second sensor to produce a second sensorsignal that has a second magnitude that varies proportionally withmovement of the second target along the second X-axis; wherein the firstand second targets are configured so that coordinated movement of thefirst and second targets within predefined limits in a directionparallel to the first and second Z-axes as the structure is moved alongthe movement axis is detectable from the first and second sensorsignals; and wherein the first and second targets further configured sothat coordinated movement of the first and second targets within secondpredefined limits in a second direction parallel to the first and secondY-axes as the structure is moved along the movement axis is detectablefrom the first and second sensor signals; and wherein the sensorassembly is insensitive to relative movement within predefined limitsbetween the structure to which the first and second sensor targets aremounted and the first and second sensors in a direction that is parallelto the Y-axes.
 2. The sensor assembly of claim 1, further comprising acontroller.
 3. The sensor assembly of claim 2, wherein the first coilhas an oval cross-sectional shape taken in a plane that includes thefirst X axis and the first Y-axis.
 4. The sensor assembly of claim 3,wherein the second coil has an oval cross-sectional shape taken in aplane that includes the second X axis and the second Y-axis.
 5. Thesensor assembly of claim 1, wherein the first target defines anaperture.
 6. The sensor assembly of claim 5, wherein the aperture isgenerally V-shaped.
 7. The sensor assembly of claim 1, wherein the firsttarget defines a ramp that is sloped along the first Z-axis.
 8. Thesensor assembly of claim 1, wherein the first target defines afrusto-conical surface that is concentrically disposed about the firstX-axis.
 9. The sensor assembly of claim 1, wherein the first target isrotatable about the first X-axis.
 10. A sensor assembly for determininga location of a structure that is translated along a movement axis, thesensor assembly comprising: a sensor mount; a first sensor coupled tothe sensor mount, the first sensor being an eddy current sensor having afirst X-axis, a first Y-axis and a first Z-axis that are orthogonal toone another, the first X-axis being disposed parallel to the movementaxis, the first sensor comprising a first coil that is wound helicallyaround the first Z-axis such that a first dimension across the firstcoil along the first Y-axis is larger than a second dimension across thefirst coil along the first X-axis; a second sensor coupled to the sensormount, the second sensor being an eddy current sensor having a secondX-axis, a second Y-axis, and a second Z-axis that are orthogonal to oneanother, the second X-axis being parallel to the first X-axis, thesecond Z-axis being parallel to the first Z-axis, the second sensorcomprising a second coil that is wound helically around the secondZ-axis such that a third dimension across the second coil along thesecond Y-axis is larger than a fourth dimension across the second coilalong the second X-axis; a first target that is coupled to the structurefor movement therewith, the first target being formed of an electricallyconductive material and being configured to interact with the firstsensor to produce a first sensor signal that has a first magnitude thatvaries in a first predetermined manner with movement of the first targetalong the first X-axis; a second target that is coupled to the structurefor movement therewith, the second target being formed of anelectrically conductive material and being configured to interact withthe second sensor to produce a second sensor signal that has a secondmagnitude that varies in a second predetermined manner with movement ofthe second target along the second X-axis; and a controller receivingthe first and second sensor signals and responsively determining thelocation of the structure along the movement axis; wherein the first andsecond targets are configured such that coordinated movement of thefirst and second targets in a first direction parallel to the first andsecond Z-axes within first predefined limits as the structure is movedalong the movement axis has no effect on the location of the structurethat is determined by the controller; and wherein the first and secondtargets are configured such that coordinated movement of the first andsecond targets in a second direction parallel to the first and secondY-axes within second predefined limits as the structure is moved alongthe movement axis has no effect on the location of the structure that isdetermined by the controller, thus rendering the sensor assemblyinsensitive to relative movement within the second predefined limits ina direction parallel to the Y-axes between the structure and the firstand second sensor targets.
 11. The sensor assembly of claim 10, whereinthe first coil has an oval cross-sectional shape taken in a plane thatincludes the first X axis and the first Y-axis.
 12. The sensor assemblyof claim 11, wherein the second coil has an oval cross-sectional shapetaken in a plane that includes the second X axis and the second Y-axis.13. The sensor assembly of claim 10, wherein the first target defines anaperture.
 14. The sensor assembly of claim 13, wherein the aperture isgenerally V-shaped.
 15. The sensor assembly of claim 10, wherein thefirst target defines a ramp that is sloped along the first Z-axis. 16.The sensor assembly of claim 10, wherein the first target defines afrusto-conical surface that is concentrically disposed about the firstX-axis.
 17. The sensor assembly of claim 10, wherein the first target isrotatable about the first X-axis.